Rheostat



.April 5, 1938. H. w. BATCHELLER 2,113,366

RHEOSTAT Filed sept. 15, 1935 f operation.

Patented Apr. 1938 PATENT OFFICE RHEOSTAT Hugh W. Batcheller, Waltham, Mass., assigner to Standard Mfg. Co., Worcester, Mass., a corporation of Massachusetts Application September 15, 1933, Serial N0. 689,585l

12 Claims.

This inventionrelates to a. rheostat, preferably with a telltale lamp included therein, the structure being characterized by a compact arrangement of parts. While rheostats of this kind may be used in various places and for various purposes, the particular embodiment of the invention hereinafter described is more especially intended for use in an electric heating circuit 'for an automobile. Heaters are desirable in cold weather, and electric heaters are frequently used,

, such heaters being supplied with current from the v'storage battery which is now a part of the equip` ment of practically every automobile.

1.5 According to the invention, I provide a rheostat automobile, each rheostat being small and compact so as to be adapted to be mounted on the dashboard or instrument panelof an automobile without occupying an undue amount of space and without being in the way. As an automobile operator, using an electric heating device in his car, is aptv to leave the car with the heater turned on, this running down the battery, I preferably equip the rheostat with.a telltale light which glows whenever the circuit is closed. This warns the operator and tends to prevent accidental neglecting of the heater circuit when, for example, the car is put away for the night. The compact and eilicient structure of my rheostat is made possible by various details of construction as appear more fully in the following description of the invention, and on the accompanying draw- Aling, of which Figure 1 is a perspective view of a rheostat with.

a telltale light, adapted to be secured to any suitable support such as a dashboard of an automobile.

Figure 2 is a sectional view of the rheostat, shown fin Figure 1, the gure also including a Wiring diagram;

Figure 3 is a section on the line 3 3 of Figure 2.

Figure-4is a section on the line 4-4 of Figure 2. Figures 5 and 6 are sections similar to Figure 4, but showingthe parts in different positions of element and a bridging conductor associatedtherewith. A

switch for controlling a'heater circuit for an (ci. zur-56) Figure 10 is a sectional view of another embodiment of the invention.

The invention may be embodied in a rheostat comprising a rotatable member I5 which, as shown in Figures 2 and 8, may consist of a cylindrical body portion I6 and a knob portion of reduced diameter, forming with the body portion I6 an external shoulder I8. The exterior surface of the knob portion I1 may be knurled as at 20 to facilitate manipulation of the knob. As shown in Figure 8, the rotatable member I5, which is preferably made of any suitable insulation material, such as a molded phenolic condensation product, rubber, glass, porcelain, or any other equivalent, may have in the rear face thereof an arcuate channel 2| which is concentric with the axis of rotation of the member I5. As shown, the arc of this channel 2| is less than 360, soY that a blank sector 22 is left on the rear face of the member I5. 'I'he member I5 is also provided with a central recess or hollow 25 inits rear face, this hollow being connected to the channel 2| as by a radial slot 26. The channel 2| is adapted to receive a 'helically coiled resistance wire 30, the channel being preferably of sulcient depth for the coil therein to be substantially ilush with the rear face of the member I5. A tong-shaped bridging conductor 3| may be provided as shown in Figure 9. This conductor may be of any suitable material such as a sheet of copper or brass having considerable resilience. The intermediate portion of the member 3| is preferably shaped into arcuate form so as partly to encircle an end portion of the coil 30. The end portions or arms 32 of the conductor 3| are adapted to pass through the slot 26, the extremities of these arms being preferably widened as at 33 to provide broad contact faces to be engaged by contact elements, these broad end portions 33 being lo' cated in the central recess 25 of the member l5. A suitable housing is provided for the member I 5. As shown, this housing may consist of a back plate 35 of insulation material, to which is secured a metal shell 36 having an inturned flange 3l engaging on the shoulder I8 of the rotatable member |5 so as to retain the member 5 loosely against the back plate 35. A pair of suitable contact elements such as binding posts and 4| are mounted on the back plate 35, each of these binding posts projecting through the plate for contact with conductors Within the casing. The post 40 is preferably alined with the axis of rotation of the member I5. 'I'his post is thus oppo-A site the central hollow 25 in which the end portions 33 of the bridging conductor 3| are located.

The end portions 33 are initially separated sufficiently so that, when the device is assembled, one of these end portions will press resiliently against the inner end of the post 40 so as to be ,n

post 4| and is arranged to press toward the member I5. Thus this contact element is always in contact either with some portion of the resistance coil 30, or the bridging conductor 3|, or the sector 22 of the rear face of the member I5, the point of contact being dependent upon the angular position of the member I5 relative to the housing. The contact means carried by the post 4I may include one or more conducting elements, a portion of which is constantly in contact with the member 4|, another portion being in contact with the member I5. or an element carried thereby. -As shown, a ball is located in the mouth of a bore 5| which extends into the end portion of the post 4I.. Next to the ball within the bore 5I is a cylindrical element 52 slidably 'fitted in the bore so as to be constantly in contact `with a side wall thereof. A helical spring 53 is seated in the' bore to press the element 52 and ball 5D outwardly so that the ball is maintained resiliently pressed toward the member I 5. Thus the ball 50 is always in contact with the surface sector 22, the conductor 3|, or the resistance element 30, according to the angular position of the member I5. Constant contact of the element 52 with the side wall of the bore in which it slides, provides a path for electrical current from the conductor 3| through the ball 50 and the element 52 to the post 4|, when the ball 50 is in contact with theconductor 3| or the coil 30. Thus only a negligible current ever passes through the spring 53'even.when relatively heavy currents are passing throughthe ball 50.

When the parts are as illustrated in Figure 4, the ball is in contact with the sector 22 of the rear face of the member I5. This is the. open switch position of the device. I f the member I5 is rotated so that the conductor 3| is brought into contact with the ball 50, as illustrated in Figure 5, then current may pass directly from the post 40 to the post 4| with practically no resistance between them. Further rotation of the member I5 results in the shifting of the resistance element 30 past the ball so that the ball 50 comes into contact with the coil 30 until the further end of the coil is reached as illustrated in Figure 6. When the parts are in the position therein illustrated, the binding post 4.0 is electrically connected to the binding post 4| through substantially the entire length of the resistance coil 30. In order to avoid longitudinal shifting of portions of the coil 30 as they rub past the ball 50, I may form the member I5 with a suitable number of ribs 55 in the arcuate channel 2|,1. each of these ribs being adapted to enter between a pair of consecutive turns in the coil 30 which is located in the channel 2|.

If the electric heater is left in operation in an automobile for any considerable period of time when the generator is not running, it is liable to in operation, I may provide a telltale light on the Arheostat so as to warn the operator `that the heating circuit is in operation. To this end the member I5 may be provided with a central bore 60, this bore including the recess 25 as a part thereof so that it extends entirely through the member I5 and is in coaxial relation therewith. As shown, the bore may have different diameters at different points. Mounted within the bore 6D is a suitable lamp socket 6|, the particular form of this lamp socket depending upon the type of lamp base which is to be employed. As shown, it is threaded toreceive the threaded base 62 of a lamp 63. The socket 6| is so arranged as to present a terminal 64 of the lamp base for contact with one of the end portions 33 of the bridging conductor 3 I. Thus one terminal of the lamp 'is constantly in contact with the bridging conductor 3| and consequently with the binding post 40. The threaded shell of the lamp base 62, which constitutes the other terminal of the lamp, is in contact with the'socket member 6|. The latter is preferably grounded in any suitable manner. As shown, a spring 10 is located in a radial bore 1|I extending through the side wall of the member I5. A ball 12 is located in the mouth of the bore 1| and bears against the outer end of the spring 10. The spring thus presses the ball outwardly and also connects the ball electrically with the socket member 5|. The ball is pressed against the metal casing shell 35, and, as the latter is preferably grounded, the lamp base shell 62 is thus grounded through the spring 10, the ball 12 and the casing shell 36. The spring-pressed ball 12 not only serves as an electrical conductor to ground the lamp base, but also may be employed as a yielding detent to hold the I5 in predetermined angular positions. To this member end, the exterior surface of the shell 36 may be i as to permit the ball 12 to enter the correspond-f y ing slot 11.01' 18 sufliciently to stop further rotation o f the member I5 in one direction. Thus Figure 4 illustrates the ball 12 seated in the slot 18 in a manner to prevent rotation in a clockwise direction. The outwardly struck element 16, however, permits counter-clockwise rotation. from this position. Figure 6 shows the ball 12 projecting into the slot 11 so as to prevent further rotation of the member I5 in a counter-clockwise direction. The slots 11 and 18 thus furnish definite limit stops for the rotation of the member I5. In addition to these limit stops, other slots or indentations may be formed in the casing to hold the member I5 yieldingly in other predetermined angular positions. One such slot is illustrated on the drawing. This slot is of suitable width to permit the ball 12 to enter a short distance, such distance being suilicient to require slight extra effort to turn the member I5 8D, as shown, is located to arrest the movement of the member I5 when the bridging conductor 3| has moved into contact with the ball 50. This enables the operator to turn the heating circuit vin either direction from suchposition. The slot-- on full by the sense of touch, since additional eiort is required to turn the member I5 beyond this point. Additional slots or equivalent recesses similar to the slot 80 may be provided at various points aroundthe circumference of the casing shell 35 to arrest the member I5 at angular positions corresponding to predetermined portions of the resistance member 30 thrown into the circuit.

The rheostat may be employed in a heating circuit as illustrated in Figure 2. As therein shown, the binding post is connected with a wire leading to a. battery which may be grounded 75 aliases heating unit 81A which is also grounded. Thus,

member |02.

when the member I5 is turned from the off position illustrated in Figure 4 to the on position illustrated in'Figure 5, the live terminal 4| is simultaneously connected to the heater element 61 and the lamp 63 through the bridging conductor 3|. If it is desired to reduce the current to the heating element, the member I5 is additionally rotated as far as desired, to bring into the circuit more and more of the resistance element 30, the limit of such motion being reached when substantially `all of the element 30 has been brought into the circuit, as illustrated in Figure 6. It is evidentthat, as long as the circuit is closed through the heater element 81, the circuit through the lamp 63 will also be closed.

Figure 1 illustrates suitable clamping means by which the rheostat may be conveniently mounted on an automobile dashboard or the-like. The casing shell 36 is provided withvan extension 90 adapted to receive the bent up end 9 I of a clamping member 192 which is also' bent up as at 93. The upstanding portion 93 maybe threaded to receive a screw 94 with a nger piece 95 at the,` end thereof, the arrangement being-such yas to permita 'dashboard or the like to be'clamped between "the upstanding portion 9| and the adjacent end of the screw 94. 'Ihe casing shell 361s preferably provided lwith a pair ofears 96 on the extension 90,'these earsbeing turned inwardly against the face of the upstanding member 9|l `in order to 'secure the rheostat to the clamping member. The casing shell 36 may also haveadditional ears 91 turned inwardly against the rear face of the back plate-35 to hold the same in position. i

Figure 10 illustrates a form of rheostat` structure diiering in certain details from that shown in Figure 2. To the back plate 35 is secured a metal housing member having an inwardly projecting flange portion I0| to retain a centrally-bored rotatable member |02 of insulation material. 'I'he housing I0| also includes a tubular portion |03 projecting from the inner edge of the-flange |02 and adapted to pass through a hole in the dashboard Aof an automobile, or other support. 'I'he tubular portion |03 may be threaded to receive a pair of nuts |04 and |05 between which the dashboard may be clamped so as to hold the rheostat tlrmly in position. A hollow metal tube ||0 is snugly but rotatably iitted in the tube |03, its inner end seating against an internal shoulder II| in the rotatable An external shoulder |I2 on the tube ||0 engages the nut 05 to maintain the' tube 0 within the housing tank |03. A lamp ||5 fits within the tube I|0, a pair of resilient tongues I6 being struck inwardly from the walls of the tube |0to clamp the base of thelamp I|5. This holds the lamp in place and provides an electrical connection for the shell ,of the lamp base. 'I'he end terminal `of .the lamp base contacts with a portion of the bridging conductor 3|. A suitable window or lens |20 of plain or colored glass may bel mounted in the outer end of the tube I|0`to protect'the lamp 5.

` 'I'he member |02 is adapted to be rotated by the tube ||0. To this end a pin I2| is mounted in the member |02 to project inwardly into the bore thereof. 'I'he inner end` of the tube Il0 is slotted to receive the pin |2|, this slot and pin connection between the member |02vand the tube l I0.causing the two to rotate together.

To limit the angle. of rotation of the member |02, an inwardly projecting lug |25 maybe provided in the wall of the housing |00, this lug riding in a rabbet or groove |26 in the periphery of the member |02, this groove being not completelycircular, but leaving a small ungrooved portion |26 of the periphery to engage the lug |25. It is evident that various modifications and changes may be made in the speciic embodiments of the inventions herein shown and described without departing from the spirit or scope thereof as dened in the following claims.

I claim:

1. A device of the class described, comprising a rotatable member having a body portion and a knob portion of reduced diameter forming an annular shoulder with said body portion, said memberhaving in its rear en d face an arcuate channelto ,receive a helical coil 'of resistance wire, a central recess, and a radial channel from said arcuate channel to said4 central recess, a coilofrresistance wire insaid arcuate channel, ai. conductor in contact with said coil adjacent to the endthereof and extending through said radial channel into said central recess, `a back plate against the rear face of said rotatable member having a central binding post constantly in contact with said conductor and a secondbinding post positioned for sliding contact with the turns of said coil as said member isrotated, a

housingy element surrounding the body portionl of said member andl securedh to said back plate. saidhousing element havingv an inturned flange engaging said sliouldero ,hold said rotatable member against'Asaidffb'lckV plate,I andv laterally .projecting means to 'limit' thelangle of rotation of said member.

2. A device ofthe class described, comprising a rotatable member having a central bore therethrough, a resistance unit arranged in arcuate iorm on the rear end dof said member, a lamp mounted in said bore, a bridging conductor connecting one of the lamp terminals with an end portion of said resistance unit, a casing for said member including a, back plate, a central terminal on said plate in contact with said bridging conductor, and a second terminal on said plateI positioned for sliding contact with said resistance unit when said member is rotated.

3. A dea ce of the class described, comprising a, rotatable member of insulating material having a central bore therethrough, a socket in said bore adapted to receive a lamp base, a casing including a back plate and a nonrotatable metal i member surrounding said rotatable member and secured to said: back plate, said metal member having a series of lateral recesses therein, a pair L,of terminal elements on said back plate insulated from said metal member and from each other, a bridging conductor connecting said lamp base with one of said terminal elements and movable into and out of contact with the other terminal element by rotation of said rotatable member, and resilient means extending through th wall of said rotatable member and electrically connecting said socket and said metal casing member, said resilient means including an element arranged to engage in said .recesses successively as the rotatable member is rotated.

4. A variable resistance device, comprising a rotatable member, a -stationary metal member having recesses therein, resilient means carried by said rotatable member and cooperating with said recesses to yieldingly holdsaid rotatable member in predetermined angular posltions,*an elongated resistance element carried by said rotatable member f or rotation therewith, a telltale lamp mounted in said rotatable member, a conductor connecting one of the lamp terminals with said resistance element, and means including said resilient means electrically connecting the other terminal of said lamp with said stationary member. I

. 5. In a variable resistance device, a stationary casing having a back plate and a cylindrical side wall with an inturned ange,ahollow member rotatable in said casing, said member having a recessed rear face bearing against said back plate and a shoulder engaging said flange to retain the member in position, a resistance element on said rear face, a central binding post on said back plate substantially alined with the axis of rotation of the member and electrically connected to an end of said resistance element, an openended lamp socket within the hollow of' said member, a lamp engaged in said socket, aresilient conductor between and in contact with the terminal of said lampand said central bindingY post, and a terminal on said casing in contact with said resilient`conductor when said member isin apredetermined angular position and in contact with various portions ci said resistance element when said member is in other angular positions.

6. In a device of the class described, a rotatable insulation member having a central bore therethrough and a rear face' with an arcuate channel concentric with said bore and a radial slot from the bore to the end of said channel, means in said bore to receive a lamp base so that a terminal element of the lamp in said socket is presented toward the rear end of the bore, a helically coiled resistance element seated in said channel, and a tong-shaped conductor gripping an end portion of said resistance coil, the end portions of said conductor extending through said slot to the axis of said bore, one of said end portions of the conductor being positioned to engage said lamp terminal. l

7. A device of the class described, comprising a rotatable member having a body portion and a knob portion of reduced diameter forming an annular shoulder with said body portion, said member having at its rear end a' helical coil of resistance wire sunk flush with the rear face of the member and arranged in the form of an arc concentric with the axis of rotation of the member, a casing including a rear portionabutting the rear face of said member and a slide portion enclosing the body portion of said member and engaging said shoulder, a central v,binding post mounted on the rear portion oi.' said casing, abridging conductor in contact with an 'end of said resistance coil and having a portion yieldingly engaging said binding post, and a second binding post mounted on the rear portion of said casing and having a contact element yieldingly pressed intocontact with said coil. K

8. A device of the class described, comprising a rotatable member of insulating material having an axial bore therethrough, a lamp socket' mounted in said bore and open at both ends, a

resistance unit carried at the rear end of said member and arcuately arranged concentrically to the axial rotation, a bridging conductor in contact with an end of said resistance unit, said conductor having resilientportions located at the center of said rear face of the rotatable member for engagement by the base of -a lamp mounted in said' socket, and a i'lxed contact element adapted for sliding engagement with said resistance unit when said member is rotated.

9. In a variable resistance device, a cylindrical metal shellhaving an inturned flange at one end, a plate of insulating material secured across the opposite end of said shell, a hollow rotatable member having a portion retained within said shell by said flange and another portion projecting beyond said flange, a pair of relatively movable elements engaged by said plate and rotatable member respectively, one of said elements being an elongated resistance element, the other said element being a contact element in sliding contact with I said resistance element, a lamp mounted within said hollow rotatable member, means electrically connecting one terminal of said lamp with said shell, means electrically connecting the other terminal of saidlamp with one of said elements, two connection terminals mounted on said plates, and means electrically connecting said connection terminals respectively with said elements.

10. In a combined rheostat and switch device, I

a housing comprising a rear wall member of insulating material and a metal member attached to said rear wall and having an aperture opposite said wall, a hollow operating member projecting through and rotatable in said aperture, said-operating member and housing including cooperating means for retaining a portion of said operating member within said housing, a pair of relatively movable elements engaged by said rear wall and said operating member respectively, one of said elements being an elongated resistance element, the other said element being a contact element in sliding contact with said resistance element, a lamp-mounted within said operating member, means electrically connecting one terminal of said lamp with said metal housing member, means electrically connecting the other terminal of said lamp with one of said elements, two connection terminals monted on said wall member, and means electrically connecting s aid connection terminals respectively with said elements.

11. In a combined rheostat and switch device,

a hollow manually rotatable member, an electriclamp mounted in the hollow of said member, a stationary housing supporting said member and from which said member projects, an elongated resistance element arranged in a. circular arc concentric with the axis of rotation of said member, a pair of connection terminals extending through the portion of the housing opposite said rotatable member, and means operable by rotation of said member to connect said lamp and a variable portion of said resistance element into a circuit including said pair of connection terminals.

12. A variable resistance device comprising a stationary casing having an opening, a hollow member rotatably supported Within said casing and` projecting through said opening, a lamp socket mounted within said hollow member and rotatable therewith, a lamp in said socket, an elongated resistance element arcuately disposed' within said casing concentrically with the axis of rotation of said hollow member, a pair of ter-A minals on said casing connectible with said lamp, and connection means operable by rotation oifA said hollow member to connect any desired portion of said resistance element between said terminals, said means including a conductor in sliding contact with said resistance element.

HUGH W. BATCHELLER. 

